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Low frequency humming sound


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#1 PJS54

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Posted 12 July 2018 - 07:59 PM

I collected my 'new' 2015 C3 Picasso Exclusive 1.6 BlueHdi today and soon noticed a low frequency humming/booming sound, which to my ears was quite loud. It is apparent at low speed and with the clutch disengaged. It doesn't stop when I touch the brakes. 

 

I drove about ten miles towards home before I made my mind up that it just didn't seem right, so drove back to the dealership, Aston Vauxhall at Melton Mowbray. I went out in the car with the same mechanic who had just serviced it and although I could still here it, Sod's Law dictated that it didn't seem quite as loud (I wondered if the extra person in the passenger seat altered the internal sound characteristics a bit). It had just been serviced and MOT'd, so he suggested that the most likely cause was tyre noise. It has Michelin Eco tyres on the back and some decent quality cheaper tyres on the front. 

 

I'm sure they were being quite genuine and not trying to fob me off in any way, but I wondered if my hearing was just better than theirs, because it was still very obvious to me. So, the question is, has anybody else experienced similar? The noise doesn't change with speed, as I thought it would with anything wheel related. Any ideas?



#2 gray

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Posted 13 July 2018 - 09:02 AM

Does it change if you 'weave' the car side to side, or on turning left/right ? (Wheel bearing suspect - although it should have been picked up on the MOT as a noisy bearing).

Try swapping the wheels around: Front/rear.

Edited by gray, 13 July 2018 - 09:03 AM.


#3 PJS54

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Posted 13 July 2018 - 09:58 AM

I really don't think it's a wheel bearing, as the technician who had only just serviced it said they were always checked. What's also odd is that I didn't notice it on my short test drive several days before, in fact I'd remarked on how quiet it seemed. Having said that, the air-con had been blasting away full bore on a hot day, which might seem slightly contradictory, but it was on when I first noticed it yesterday. I've had noisy tyres before, but I've always had to get up to a fair old speed before it became really apparent. This is noticeable more or less as soon as the car is moving. The noise does fluctuate but only quite subtly. One way I might describe it is by comparing it to somebody blowing across the end of a metal tube to produce a very low frequency sound. There's a steel gate post on a local nature reserve that makes that kind of noise in the wind. :)

 

If I'd have bought the car privately I'd be fearing the worst, but in this case I really do feel quite confident that they aren't trying any tricks, as they seem very professional and have a good reputation to maintain. They told me that they'll be very willing to change the tyres round to see if that helps, so I might go back as a last resort. It's 30 miles from where I live, but at least it's a pleasant drive. One word of warning though – never, ever go to Melton Mowbray on a market day, as it's sheer hell.



#4 PJS54

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Posted 13 July 2018 - 02:01 PM

All tyres were thoroughly tyre-painted, which has possibly highlighted that there is uneven wear on the front ones. I'm not yet sure if that is possibly due to them being slightly over inflated, but I have to go out, so I'll have another look when I get back and if it looks worthy of comment I'll post a pic later on. It's definitely a noise that shouldn't be there.



#5 Avon

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Posted 13 July 2018 - 03:42 PM

Very much a long shot but are all the windows shut tight?

 

Usually quite a bit of resonance if a back one is just down a fraction, costs nothing to wind them all open and then shut making sure there are no obstructions.


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#6 PJS54

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Posted 13 July 2018 - 05:55 PM

Yes – I thought of that. I've just complete another 25 miles and it's starting to get on my tits now. I've now established that I can hear it clearly at 10mph in neutral, which must surely rule out bad tracking and tyre noise. Imagine a slow, very low-pitched woo-wooing sound, which could be coming either from the wheels, the typres or even being transitted through the floor pan. It's one of those noises that's impossible to pin down when you're in the driver's seat, as I've found in the past when being driven mad by an annoying squeak.

 

Come on all you experienced super-brains out there; just give me something to suggest to the mechanics when I take it back. I wish I still had a big trolley jack like I had years ago, because I'd lift the wheels up and spin them. I feel sure it must be possible to hear something, but I can imagine how embarrassing it will be if I ask them to do that and there's nothing apparent. What on earth can it be that makes such a deep sound at 10mph?



#7 gray

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Posted 13 July 2018 - 08:34 PM

Aircon Fan on high speed  ?  Interior fan ?

 

Turn as much 'stuff' off as possible.  See if it's still there.  :)

 


Edited by gray, 13 July 2018 - 08:35 PM.


#8 ChrisGibbard

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Posted 13 July 2018 - 11:47 PM

You are not going to solve this on your own. Get 3 mates and all of you go out for a drive and find out where the noise is coming from. As gray said turn everything off, might get a bit hot and sweaty with no aircon, but if you cannot find it, take the car back to the dealer and get them to sort it out. Or just give up and get your money back.



#9 PJS54

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Posted 14 July 2018 - 11:52 AM

I should have said that it's still present with the aircon turned off. Any such noises seem to come from the rear nearside when you're in the driving seat, but although I hear it mostly through my left ear; it almost feels as if it's being transmitted through the body of the car.



#10 Avon

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Posted 14 July 2018 - 02:35 PM

Try trapping a sheet of paper in the door, at all points and in each door and hatchback. I wouldn't be suprised if one of them is a loose fit especially around the window area.


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#11 granpa

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Posted 14 July 2018 - 03:02 PM

Ok, my short romance with a C3 pic was ended as I couldn't stand the constant transmission drone that was more apparent as a vibration than a noise, could feel it through the pedals and the steering at any speed, any gear, it was ex-mobility import from Ireland, not too old and moderately low mileage, but not for me



#12 PJS54

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Posted 14 July 2018 - 03:26 PM

Next episode in this hopefully not too long-running saga: I jacked up one back wheel at a time, using the supplied jack with the ergonomically bizarre handle and spun the wheels by hand. Is it normal to be able to hear the brake pads scaping at all when there are no brakes being applied (handbrake also off, before somebody asks)? It's not enough to cause much resistance, but quite audible and I've noticed that quite a lot of sticky black dust has coated the insides of the wheel blades after only a few days. I WILL get to the bottom of this.

 

I don't think it's a transmission drone, because if it was that, I don't see how anybody would ever find it acceptable. It's such a low frequency sound when inside the car, that it seems to get right inside my head. I'd have to turn the radio up very loud to mask it.

 

And no, it isn't tinnitus – I've already established that.  :lol:


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#13 PJS54

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Posted 15 July 2018 - 10:42 AM

Here you go. Turn the volume up loud.

 

 



#14 PJS54

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Posted 15 July 2018 - 11:04 AM

I should have mentioned that you will probably need to listen through speakers capable of reproducing the sound. I tend to forget that many people tend to view websites by using phones.



#15 PJS54

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Posted 15 July 2018 - 03:15 PM

I'm now fearing the worse, as I can hear it in this video (especially at 10:20 onwards). The test driver doesn't mention it at all, which seems strange to me because I find it very off-putting. I'm hoping it isn't something endemic to these models due to the design, or it seems that I'll be stuck with it.

 

 



#16 nightmail

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Posted 16 July 2018 - 05:09 PM

I think it could be tyre related. The O/E tyres are very expensive Bridgestone extra load type. Guessing dealership/ previous owner have fitted lower spec tyres which don't suit the car and if not XL will be contravening C&U regs.

 

 

 



#17 stimulator

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Posted 17 July 2018 - 05:55 AM

The tyres on my C3 pic were Michelin energy. The car was quiet, a bit crashy over some bumps. My new C3 saloon isshod with Goodyear tyres and is very quiet on them.
Some will say that mixing tyre makes is not a good idea as different tred patterns on them makeing different noises. This could be your problem that the sound frequency given off by them is producing the annoying noise due to interference of the sounds cancelling out parts which leave the noise you hear. But difficult to explain. To check that you need to find some who will lend you four wheels with same tyres on to fit and run.
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#18 Lancelot

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Posted 17 July 2018 - 11:53 AM

Have you tried running them 2psi under the correct pressure?


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#19 ArthurM

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Posted 17 July 2018 - 03:53 PM

I noted in your post 6 that the noise is noticable at only 10mph.Does the noise get faster the quicker you go?

Having watched the video made by the seller,I must say that I could not hear the noise you notice. There was road noise and some sound from the roof bars.

What did concern me was the yellow warning light that came on at 0851 on the video and the driver not noticing it at the time.



#20 PJS54

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Posted 17 July 2018 - 04:16 PM

I noted in your post 6 that the noise is noticable at only 10mph.Does the noise get faster the quicker you go?

Having watched the video made by the seller,I must say that I could not hear the noise you notice. There was road noise and some sound from the roof bars.

What did concern me was the yellow warning light that came on at 0851 on the video and the driver not noticing it at the time.

 

The noise remains constant. The first video was of my car, the second, professional one was of an entirely different car that I insluded to make a point. I can hear the noise clearly on both, but I'm listening through some add-on Labtec PC speakers. I doubt if laptop speakers are capable of reproducing the frequency.

 

Anyway, I took the car to my nearest Citroen service centre and the mechanic who sat with me heard the noise almost immediately and thought he knew what it was. Sure enough, he asked me to run my hand one way alonh the tread (smooth) and then in the other direction, when I could feel the ridges at the edges of the tread. The tyres are scuffing due to wheel misalignment, but I'm surprised they make so much noise when the car is barely rolling.

 

I phoned Aston Vauxhall and it seems they don't have the necessary equipment there to re-align the wheels, so will have to take it to a nearby specialist. However, there is a caveat; they will only pay for it if the wheels are outside the acceptable, permitted tolerances. I hope I'm not in for a battle here, because the tyres are clearly scrubbing and if left as they are will have a very short lifespan.